No prices on here. Not a DIY site
You can usually get a full system for that much.
If you paid upper 4 figures for a furnace only install, you got ripped off unless you need ot remove a wall or rent a large crane ot install it... yes, it happen in commerical & indsutrial.
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A ID fan should not have failed within 10 years, but again, it's probably oversized and short cycling, so there's a LOT of wear and tear on that fan. Start & stops are what wear out motors faster, not runtime.
Few dealers will be insterested in selling you parts. Feel free to search online. You can get ballpark prices for furnaces, you might even find your part and some p*** p*** instructions on how to install it fomr some DIY site.
You'd be money ahead to just replace your furnace with a new, properly size high effciency unit and save 15% on your gas use, more depending on how oversized it is now.
FYI, I can heat my whole 3200sqft home with just 70k BTU's at 0F outdoor temp and it's only average insulation with a lot of windows. If it burnt down tommorrow and I rebuilt it to my specs, it would need 1/2 that, mostly due to ventilation requirements.